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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 51 |
| 4 | 1115 |
| 5 | 34265 |
| 6 | 1318699 |
| 7 | 60477844 |
| 8 | 3210707626 |
| 9 | 193589241468 |
| 10 | 13070085476528 |
[1,4,51,1115,34265,1318699,60477844,3210707626, 193589241468,13070085476528] |